Press fittings are used for connecting pipes and/or fittings, wherein a permanently pressed and optionally non-releasable connection between the fitting and the pipe and/or the fitting can be produced by cold forming the fitting and with the aid of a seal. In addition, purely metallic connections are also known in which the fitting and a part of the pipe and/or fitting to be connected are deformed.
Field of the Invention
For pressing the press fitting, pressing tools are used which convert a linear force generated hydraulically or electrically into a pivoting movement of two pressing jaws that are movable relative to each other. For this purpose, on the one hand pressing jaws connected directly to the pressing tool can be provided, which are applied to the press fitting and then press it by compression. On the other hand, in particular in the case of larger dimensions of the press fitting, a pressing loop comprising at least two segments and two pressing jaws connected to the pressing tool can be provided, and these press the segments of the pressing loop and therefore press the press fitting.
Press fittings for pipes with large dimensions of, for example, more than 50 mm up to more than 150 mm external diameter, require both a large pressing force and a large pressing distance during pressing, however. It is only in this way that fittings with the pipes to be connected can be sufficiently deformed and reliable connections can be produced.
The work requirement for deforming such a large press fitting frequently exceeds the working capacity of the commercially available pressing machines, which are, for example, capable of ensuring a work of 32 kN*40 mm stroke or 45 kN*45 mm stroke. Accordingly, in the case of large dimensions, it is not possible to press the press fitting by means of a single pressing machine stroke. Multiple application of the pressing machine leads to an intermediate loss of pressing force and therefore the elastic pre-tension on the press ring, as a result of which the pressing process is impaired overall.
Description of Related Art
A two-stroke clamping jaw is known from the prior art of EP 2 522 464 B1 in order to counter this problem. However, the construction of the two-stroke clamping jaws is complex and therefore difficult to transfer into series production and construction site application. Furthermore, the elastic pre-tensioning of the press ring and the clamping jaw is lost in this system between the first and the second press-machine strokes. Correspondingly less working capacity is available for the overall deformation.